The present invention relates to optical fiber having a silica filament core and a thermoplastic cladding which has an index of refraction lower than that of the core.
Optical fibers are well known in the art for transmission of light along a length of filament by multiple internal reflections of light. Great care is taken to minimize light losses along the length of the filament, or, in other words, internal reflection is made as close to total as possible so that light applied to one end of the optical filamentary material is efficiently transmitted to the opposite end of the material. The light transmitting portion or core of the optical filamentary material is surrounded by a cladding having an index of refraction lower than that of the core, so as to minimize the escape or absorption of light along the length of the filament. This cladding is normally chosen to be transparent since an opaque cladding tends to absorb light.
An important consideration in formation of optical fibers is minimization of any factor which increases the attenuation of transmitted light within such fiber.
Where low attenuation of transmitted light in an optical fiber material is critical, the preferred material for the filamentary core is silica, since it has one of the lowest attenuations presently known. Suitable cladding materials known in the art include thermoplastic polymers which have an index of refraction lower than that of the core; and which preferably are substantially amorphous.